1. Field
The present invention relates to a double-sided emission type display device.
2. Description of the Related Art
Flat panel display devices are being used as display devices instead of cathode-ray tube display devices due to their properties such as light weight and thin profile. Representative examples of such flat panel display devices include a liquid crystal display (LCD) device and an organic light-emitting diode (OLED) display device. The OLED display device has advantages that it has excellent brightness and viewing angle properties, compared to the LCD device, and it may be implemented as a super-thin type of display device because it does not require a backlight.
The OLED display device is a display device that forms excitons through the recombining of holes and electrons, respectively, injected through a cathode and an anode on an organic thin film and uses a phenomenon in which light with a specific wavelength is generated by energy from the formed excitons.
The OLED display device is classified into a passive matrix type and an active matrix type according to a driving type, wherein the active matrix type of display device has a circuit that uses a thin film transistor (TFT). The passive matrix type of display device has an advantage of being easier to manufacture because a display area primarily includes a matrix of crossing cathodes and anodes to form pixels. The use of passive matrix display devices, however, tends to be limited to low-resolution images and small-sized displays, and passive matrix displays typically require a higher driving voltage, and have a lower material life. The active matrix type of display device may have a more stable brightness, because each pixel of the display area has a TFT and constant current is supplied to each pixel. In addition, the active matrix type of display device typically has a lower power consumption than the passive matrix type of display device, which is an important factor for implementing high-resolution and large displays.
An OLED display device may display images on both sides. In double-sided emission type OLED display devices, a backside emission type of organic light-emitting elements may be located in each of a first substrate and a second substrate, and the first and second substrates may be arranged to face each other. In this case, TFTs for controlling the driving of the organic light-emitting elements are located on the substrates in which the organic light-emitting elements are located. The backside emission type means that light from an organic light-emitting layer is emitted to the outside through a TFT.